When watching visual content (for example, reading, watching video content, or looking into a mirror), a user often experiences interference from light signals sent by other light sources in the environment where the user is located. For example, in a scenario shown in FIG. 1, when a user watches content displayed on a display screen of a terminal device (such as a mobile phone, a portable computer, or a television, etc.) 110, light emitted by a light source 120 is reflected from the surface of the display screen of the device 110 to the field of view of the user. When the strength of the light signal of the light source 120 reaches a certain level, the user watching the content experiences the interference.